Radioresistance of Five Strains of Clostridium Botulinum in Selected Food Products^a,b

Abstract

SUMMARY Spore recovery counts made on five strains of Clostridium botulinum indicated striking differences in radioresistance. Strain 12885A was most resistant, and strain 32B least resistant. A difference was noted in the survival of spores in five food products (green beans, chicken, codfish, pork, and beef), with green beans providing the most destruction. It was also observed that a given substrate was found to allow a greater per cent survival of one strain than another, so that two strains compared in one food do not always show the same relationship as when compared in another food. Some evidence indicates a modest recovery of viability of the irradiated spores during frozen storage prior to culturing. Since the character of the food determines in part the dose required for the destruction of Cl. botulinum, no single dose would be best for all food products.

Cryogenic gamma irradiation of prototype pork and chicken and antagonistic effect between Clostridium botulinum types A and B

“…Proctor et al (31) inoculated sterile boneless chicken (with skin) with C. sporogenes (390 spores/sample), irradiated the food with electrons at -29°C, and then assayed for survivors and computed D37 values. As in Wheaton's study (43), the D values (D = 2.303D37) of the organism decreased (2.32, 0.66, and 0.48 Mrad) with increasing doses (0.23,0.47, and 0.70 Mrad, respectively), although sterility was achieved with a dose of 1.86 Mrad. Yet when they irradiated uninoculated nonsterile controls with 1.86 Mrad, they found indigenous viable anaerobic bacteria (43/g) but not the putrefactive variety; standard plate counts were <300/g.…”

Comparative Resistance of Strains of Clostridium botulinum to Gamma Rays1

“…The most resistant cultures were represented by strains 33A, 36A, 40B, 41B, and 53B, with D values in the range of 0.317 to 0.336 Mrad; the group with intermediate sensitivity, 62A, 77A, 12885A, and 9B, had D values of 0.224 to 0.253 Mrad; the most susceptible strain studied, 51B, had a D value of one-half to one-third that of the most resistant strains (0.129 Mrad). Wheaton et al (1961) observed that the individual radiosensitivity of five strains of C. botulinum suspended in each of five foods varied with the foods, but the relative order of resistance between these cultures was unchanged. In accordance with their findings, it is believed that the relative order of tolerances between the three groups of organisms in Table 5 would also remain unaffected in various food substrates.…”

Radiation Sterilization of Prototype Military Foods. III. Pork Loin

“…Schmidt and Nank (13), using a mixture of three type A and two type B strains totaling about 108 spores per dose, obtained nonswollen, nontoxic, sterile cans when irradiated to 2.70 Mrad at 26.7 C and incubated for 12 to 15 months at 29.4 C. The minimal radia-tion dose (MRD), or the equivalent theoretical 12D dose, was 3.30 to 3.60 Mrad. Wheaton et al (15) found that 2 X 108-9 X 101 spores per can of ground pork, or 6 X 109-27 X 109 spores per dose, of their most radioresistant C. botulinum strain was reduced to 0.4% of the original inoculum when irradiated at -29 C to 1.7 Mrad, the highest dose tested. Since product incubation of the inoculated cans was not carried out, partial spoilage or end point data were not available, hence, computation of a 12D dose seems unjustified.…”